Electrical protective system



Sept. 27, 1932. L. K.ISWART ELECTRICAL PROTECTIVE SYSTEM Filed Aug. 22. 1950 INVENTOR ,LZESwar TORNEY Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE" LELAND K. SWART, OF MOUNTAIN LAKES, NEW JERSEY, ASSIGNOR T AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPQRA'IIOIh OF NEW YORK ELECTRICAL PROTECTIVE SYSTEM Application filed August 22, 1930. Serial No. 477,170.

This invention relates to electrical protective systems. More particularly, this invention relates to arrangements for simultaneously grounding a plurality of circuits when induced voltages become impressed thereon.

A pair of protective blocks each having an air gap which breaks down at a predetermined potential have recently been used in the telephone art for. the protection of each of a number of telephone circuits from high voltagesset up therein by one or moresources extraneous to the circuits themselves. these arrangements a resistor or a saturating reactor are interposed in the ground connection of each pair of such protective blocks. The resistor or the reactor, as the case may be, carries the operating current of the two blocks. associated therewith. In these arrangements moreover, the impedance drop across the-resistor or the reactor is rectified by a rectifier of the copper oxide type. The rectified current is applied to a relay employed to shunt both protective blocks so that any induced current or currents may be carried through the heavy duty contacts of the relay.

A plurality of pairs of protective blocks and a pluralityof relays,one corresponding to each of the pairs of protective blocks, have been associated with a plurality oftelephone circuits running substantially parallel to each other, each exposed to the same inductive effect. Apparentlyit will be possible to have'a condition where some of the various relays will be operated and some unoperated, because the inductive effect may not be sufficiently large to cause all of the associated protectiveblocks to become operated. This condition creates a great hazard, since the circuit connected to the protective blocks and relays which have been operated will be at ground potential, While the circuits connected'to the protective blocks and circuits which have not been operated will be at potentials considerably above ground. 1

The copper oxide rectifier forming part of the protectiveequipment of the prior art has been found to be unsatisfactory. The characteristics of there'ctifier change with age. Moreover, this rectifier does not return to its original state after a severe application of voltage or the passage of a large current and, furthermore, its characteristics change with temperature variations. All of these matters substantially affect the sensitivity of the device and reduce its range of operation.

- One of the objects of this invention is to provide an arrangement for simultaneously grounding a plurality of conductors or circuits when an extraneous inductive efiect becomes induced in any one of the conductors or circuits.

Another object of this invention is to associate a relay arrangement acting as a rectifying system with a plurality of conductors or circuits all of which may be exposed to substantially the same inductive efiect-s so that any voltages impressed uponv an associated resistor or reactor will causethe simultaneous grounding of all of the conductors or circuits.

l/Vhile this invention will be pointed out with particularity in the appended claims, the invention itself will be better understood from the detailed description hereinafter fol lowing when read in connection with the accompanying drawing showing two embodiments of the invention merely for the purpose of illustration, Figure 1 of which includes two relays, one acting as a rectifier of impressed current and continuously operating the other relay. Figure 2 also includes two relays, the first having an armature which vibrates at the frequency of impressed current and maintaining the second relay continuously operated with current derived from an associated battery.

Referring to Figure 1 of the drawing, the

reference characters lV /V ,lV and W represent four of a plurality of conductors or circuits all of which may be supported by a common protector pole. Each of these conductors may be connected to ground through a protective block and a common resistor or a reactor or a transformer, a reactor or autotransformer designatedL being employed herein merely for the sake of illustration. The various protective blocks are designated P P P and P One terminal of each of these blocks is connected to an arm or contact associated with the reactor L, which is shown as Variable. Each of the protective blocks P P P and P may include two carbon electrodes spaced from each other by a gap of, for example .005 inch. The two electrodes may be sup orted in a'porcelain holder which is so shaped as to insure the normal existence of a gap of predetermined width between the component electrodes. 7

The reactor L is connected in series with a condenser designated C and with the windings L and L of a master relay designated R windings L and L being arranged in parallel relationship. RelayR which may be of the polar or other type, has its armature normally spaced from its contacts K and K It is to be understood, however, that a single winding may replace windings L and L within the scope of this invention.

The contacts K and K are connected in series with the windings L and L of a relay designated R Relay R may be of the slow release type, if desired. Condensers C and C shunt windings L and L respectively, and these condensers are preferably of large capacity. The armature of relay R is normall separated from its contacts K and K A attery designated B which may be composed of a plurality of drycells, is connected in series with contact K and with the wind-' ings of a plurality of relays two of which are shown for the purpose of illustration and designated R and R the windings of these relays being arranged in parallel. relationship and: being. designated L and L respectivelly. Each of the contacts of the relays R and; 4 extends toone of, the conductors W W W or, W Thus, the contacts of relay B extend to conductors W and W and the contacts of relay R extend to conductors W and W Moreover, the fixed terminals of the. armatures of, relaysR and R are connected in parallelto groundthrough a portionof the.

reactor. Lo.

. Whenv an. extraneous voltage becomes, in.- duced in, any one. or more of the various conductorsorcircuits W 'W' W3 orW the. protective block or blocks associatedwitli the circuit or circuits so impressed will, dis- 1 chargea substantial current, and that current will flow through the lower portion of reactor.

L to ground. A somewhat higher voltage will send acurrent through condenser C tothe windings L and L of. relay R the condenserfunctioning. to reducethe time required to buildup a substantial current in these windings. The. armature of: relay R will vibrate at the frequency of the impressed current, audit will alternately close contacts K andK- It may-be assumedfor the purpose of illustration that contact K will be closed. during. the. positive portion of each cycle, and contact K during the negative portion. Current will flow through winding 173.0f relay R when. contact K is closed,

and through winding L when contact K is closed. WVindings L and L are wound so as to maintain the armature of relay R closed against contact K while the armature of relay R remains in vibration between contacts K and K Condensers C and C receive charges which aid in holding the armature of relay R against contact K while relay R is in operation. Condensers C and C moreover, decrease the time required to build up magnetic fields in windings L and L, of sufiicient strength to opcr ate the armature of relay R When contact K is closed, battery B will transmit current to the windings L and L of relays R and R respectively, and this current will divide equally therebetween. The armatures of relays R and R. will be simultaneously attracted and, therefore, conductors W W2, W and W will be promptly connected to ground through the circuits established by the armatures of these relays and the lowerportion of the reactor L The speed of operation of the arrangement shown in Fig. 1 is a function of the value of the current discharged through any one or more of thevarious protective blocks. The higher the current, the faster will relays R and R- operate. Moreover, relays R and R will operate at a speed depending upon the voltage of the battery B.

The arrangement shown in Fig. 2 is somewhat similar to the one shown in Fig. 1, both arrangements depending upon the vibration of the armature of relay R for operating the relay B In Fig.- 1- the armature of relay R acts somewhat as arectifier, for ourrentflows through windings L and L of relay R unidirectionally. In Fig. 2, however, the vibration of the armature of'relay R permits condenser C to be charged; and discharged' and the armature ofrela R remains closed throughout the perio the armature of' relay R is in. vibration, and

moreover, throughout the interval during ing, if desired. T ese pairs of'windings shown are however, in series with battery B and with the armature of relay R and its contacts, both. of: which are tied together. Condenser- C is bridged between contacts K and K and the armature of-relay R Any voltage impressed'upon any one of the various protective blocks- P Pg, P or P sufficient to bridge the gap thereof will cause current to flow through the reactor L fromits movable contact to its lower terminal aka or ground. The voltage across the outer terminals of the reactor L will cause current to flow through condenser G as well as through windings L and L of relay R which are in parallel relationship. The armature of relay R will vibrate between contacts K and K at the frequency of the impressed current.

When the armature of relay R is separated from both contacts K and K condenser C will be charged to the voltage of battery B, but the charging current per se will be insuflicient to cause a magnetic effect on windings L ,'L L and L sufficient to move the armature of relay R to contact K Then contact K is closed by the armature of relay R current will flow through battery B through windings L L L and L and contact K of relay R will be closed by its armature. The charge of condenser C will then be substantially decreased and the charge will become negligible in value. When the armature of relay R departs from contact K battery B will again charge condenser C and tend to maintain the armature of relay R closed against contact K by virtue of the magnetic fields produced about windings L L L and L of relay R by the charging current. The action of condenser C aided by the slow releasing property of relay R will tend to maintain the armature of relay R closed against contact K WVhen the armature of relay R closes contact K current will flow from battery B through the windings L L L and L of relay R and the condenser G will again be discharged. And

' so it continues, the vibration of the armature of the relay R between its contacts K and K causing the armature of relay R to maintain its contact K closed.

\Vhenever the contact K is closed, battery B will send current through the'windings of relay R and R which are connected in parallel relationship. Thus, it will be'noted that battery B not only energizes windings, L L L and L of relay R and charges condenser C but it also supplies the current required to operate relays R and R VVhe'n relays R and R are operated, the armatures of these relays will cause the simultaneous grounding of the conductors of circuits W 2, VVS and W through the lower portion of the reactor L The circuits forming the basis of this invention may be used for a line of any desired number of wires, only four of which are shown, and moreover, these circuits will operate even when a very small current 4 of an ampere or less) passes over any pair and through any protective block to ground. Furthermore, there will be no damage to the protective block or to any part of the circuit when a very large current (10 amperes or more) is transmitted over any pair or through any protective block. Thus, the circuits described herein have great advantages over those eniploying copper oxide rectifiers, and these circuits do not have the inherent variability of the copper oxide devices. All of the wires of the pole line of the arrangement forming this invention will be simultaneously grounded even when a small fraction of an ampere is transmitted through a protective block, and the short circuiting action will occur within the time corresponding to one or two cycles, especially if the voltage of the battery is not too low. Inasmuch as the arrangement of this invention operates with great speed, the time during which any one of the protective blocks may be burned is greatly reduced and hence the useful life of these blocks before becoming pitted and permanently grounded, is extended materially. Such speedy operation, moreover, reduces the time during which an acoustic shock may be experienced and only a single transient impulse may reach a receiver.

While this invention has been shown and described in certain particular arrangements merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. The combination of a plurality of sig nal circuits which are exposed to extraneous inductive effects, a plurality of protective blocks each associated with one of said circuits and operated to discharge a substantial current when a voltage exceeding a predetermined value is impressed upon the associated circuit, means for receiving the current discharged by any protective block, relay arrangements for deriving direct current from the current present in said receiving means, and means responsive to the directcurrent for simultaneously grounding all of said circuits.

2. The combination of a plurality of signal circuits exposed to extraneous inductive effects, a plurality of protective blocks, each protective block being associated with one of said circuits and discharging a current when an induced effect of predetermined voltage is impressed thereon, a reactor upon which is impressed the current so discharged, a first relay connected to said reactor and having an armature which vibrates at the frequency of the current impressed on the reactor, a second relay which becomes operated when the armature of the first relay is in vibration, and means controlled by the second relay for simultaneously grounding all of said circuits.

3. The combination of a first relay having a winding which receives alternating current and an armature which vibrates between two contacts at the frequency of the received current, and a second relay having two windinas Connected in series with each other and with the two contacts of the firstrelay, the armature of the second relay remaining closed as long as the winding of the first relay receives alternating current.

4. The combination of a first relay having awinding which receives alternating current and an armature which vibrates between two contacts at the frequency of the received cur Iii rent, a second relay having two windings connected in series with each other and with the two contacts of the first relay, the armature of the second relay remaining closed as long as the winding of the first relay re- IB' ceiVes alternating current, and two condensers each in shunt with one of the windings of said second relay.

5. The combination of a first relay having a winding which receives alternating current Q and an armature which vibrates between two contacts at the frequency of the received current, a second rela having two windings con nected in series with each other and with the two contacts of the first relay, two condens- 2 cm each in shunt with one of the windings of the second rela and a circuit controlled by the armature o the second relay, said circuit remaining closed only as long as the winding of the first relay receives alternating current. In testimony whereof, I have signed my name to this specification this 20th day of August 1930.

- LELAND K, SWART. 

